The present invention is related to a method for producing a powdery intermetallic compound having particle size of a few to tens .mu.m.
Powderized metallic material has been used for manufacturing a product having an objective configuration by a sintering method or the like. A proper metal working process may be applied to a sintered body to be formed into a final shape. The same metal powder has been used as additives to resin or rubber compositions for manufacturing electric conductive paint, a magnet volt, etc. Such powdery metallic material has been prepared by mechanical crushing, oxidation-reduction, atomizing, etc.
For instance, a powdery intermetallic compound Nb.sub.3 Al useful as a superconductive material is prepared from an alloy bulk having the same composition as an objective composition by a plasma rotary electrode method, HDHP process using reducing reaction with hydrogen, etc. The powdery intermetallic compound Nb.sub.3 Al may be prepared by a mechanical alloying process wherein pure Nb powder is alloyed with pure Al powder by mechanical stirring.
A powder metallurgy process is suitable for manufacturing a product comprising a high-melting point intermetallic compound, as compared with a melting process. In this consequence, it is required to offer finely powderized material at a low cost with high productivity. However, it is difficult to obtain a powdery product having uniform composition and proper particle size distribution with high productivity according to the conventional powderizing methods. In addition, some of the conventional methods need a huge cost of equipment.
In case where a finely powderized intermetallic compound is to be produced by the plasma rotary electrode method, it is difficult to prepare a rotary electrode made of the intermetallic compound due to the brittleness of raw material. That is, there is a problem to be overcome for adopting the plasma rotary electrode method in a mass production line. In addition, the powder obtained by this method has particle size distribution over such a broad range that the powder being compressed exhibits poor compactibility. As a result, it is difficult to obtain a compressed powdery body or a sintered body having high density.
It is reported that powdery intermetallic compound Nb.sub.3 Al can be pulverized by applying mechanical impact force to the alloy bulk which has adsorbed hydrogen therein (see Journal of the Less-Common Metals, 158 (1990) p. 71-79 and 139 (1988) p. 97-106). The intermetallic compound particles are reformed into the state of brittle hydride by the adsorption of hydrogen. The brittle hydride can be crushed into finely pulverized state by mechanical impact force. According to this method, a raw material to be used must have very fine particle size, since the adsorption of hydrogen is necessary to make the raw material brittle. Consequently, the finely pulverized product is not obtained with high productivity. In addition, expert skill is required for the manufacturing process.